This application claims priority of Japanese patent application number 2000-082995, filed Mar. 23, 2000.
1. Field of the Invention
This invention relates to a wafer polishing apparatus. More particularly, this invention relates to a polishing apparatus, for semiconductor wafers, using chemical mechanical polishing (CMP).
2. Description of the Related Art
Miniaturization of ICs (integrated circuits) has made progress in recent years, and IC patterns are being formed in multiple layers. A surface of the layer on which such a pattern is formed unavoidably has an unevenness to a certain extent. According to the prior art technology, a pattern is formed on a previous layer. However, the greater the number of layers and the smaller the widths of lines and the diameters of holes, the more difficult it becomes to form satisfactory patterns and the more likely it becomes for defects to occur. Therefore, it is a customary practice to planarize the surface of a layer having a pattern formed thereon and then to form the pattern of a next layer. A wafer polishing apparatus (CMP appartus) using a CMP method has been employed for polishing a wafer during the formation process of such an IC pattern.
The wafer polishing apparatus according to the prior art. includes only one platen. Therefore, when two-step polishing of the wafer is conducted, polishing of the wafer is first done by using specific slurry and is then done by changing the slurry. However, since the platen must be washed before the slurry is changed, polishing time is wasted and work efficiency is low.
A wafer polishing apparatus is also known that includes two or more platens and can change polishing characteristics for each platen. However, the wafer polishing apparatus carries the polished wafer to a next platen while the slurry used in a previous step remains adhering to the wafer, and polishing cannot be carried out satisfactorily. Alternatively, two-step polishing is conducted by carrying the polished wafer to a washing unit, and then carrying the washed wafer to a next platen. In this case, a loss occurs in the polishing steps and the polishing time becomes long because the wafer is carried into the washing unit whenever it is polished.
In view of the problems described above, it is an object of the present invention to provide a wafer washing apparatus capable of conducting high-precision multi-step polishing without inviting any waste in the polishing steps.
To solve the problems described above, a wafer polishing apparatus according to the present invention incorporates two or more platens in a polishing unit and includes injection ports for washing water at the boundaries between the platens. When two-step polishing of the wafer is carried out, washing water from the injection ports can wash the wafer while the as-polished wafer is held and conveyed by the polishing head to the next platen. Therefore, the wafer polishing apparatus can prevent slurry, etc, adhering to the wafer from being carried to the next polishing step, and can execute high-precision wafer polishing. The atmosphere inside the platen of the next polishing step is not contaminated, either.
Furthermore, the wafer polishing apparatus can execute multi-step polishing without a necessity for carrying the wafer to the washing unit whenever polishing is complete, and the time lost in the polishing step can be minimized.
The present invention may be more fully understood from the description of the preferred embodiment of the invention set forth below together with the accompanying drawings.